Figure 1
Laboratory protocol. Arriving two hours before their usual bedtime, subjects spent five nights and four days in the laboratory. This figure displays the time of urine collections (shown in red), which began after the last voiding before morning (most participants urinated during the night) and continued through the final morning voiding after the next consecutive night, slightly more than 24 hours.
Figure 2
Experimental Light Treatments. Volunteers were randomly assigned to three four-hour light treatments (detailed in this figure) administered on four consecutive days against a background of <0.5 lux during eight-hour sleep periods and 50 lux during 16-hour wake periods. Treatment A was two hours at 3,000 lux from 1–3 hours and 13–15 hours after arising. Treatment B was four hours at 3,000 lux from 6–10 hours after arising. Treatment C was four hours of dim red light placebo from 6–10 hours after arising. Note that the center of each treatment was eight hours after arising, and the abscissa was hours after usual wake time.
Figure 3
Determining Urinary aMT6s Acrophase. An example of analyzing urinary aMT6s is shown. The yellow area shows that the excretion rate of aMT6s from one voiding to the next was associated with each interval between voidings. The red line shows that a best-fitting cosine curve was estimated. The salmon dotted line indicates the mesor (the mean level of the fitted cosine). The rose arrow shows that the amplitude of the rhythm is the level of the peak of the fitted cosine above the mesor. The lavender arrow shows that the acrophase is the time of the peak of the fitted cosine referenced to the prior midnight.
Table 1
aMT6s acrophase and measures of circadian malsynchronization and phase dispersion in older (n = 60, ages 60–79) and young volunteers (n = 30, ages 20–40), mean and SE.
| Age Group | Baseline aMT6s Acrophase | Final aMT6s Acrophase | Baseline Circadian Malsynch. | Final Circadian Malsynch. | Baseline Circadian Dispersion | Final Circadian Dispersion |
| Older | 4.01 ± 0.25 | 4.68 ± 0.28 | 1.57 ± 0.16 | 2.19 ± 0.19 | 1.53 ± 0.15 | 1.60 ± 0.18 |
| Young | 4.14 ± 0.23 | 5.07 ± 0.28 | 0.69 ± 0.11 | 1.09 ± 0.23 | 1.04 ± 0.12 | 1.10 ± 0.20 |
Figure 4
Phase Response Plots for each Light Treatment. Shown are the shifts in aMT6s acrophase, which varied significantly for each treatment, as a function of the circadian timing of the light treatments, defined as the center of treatment (eight hours after arising) relative to the aMT6s acrophase at baseline.
Figure 5
Circadian malsynchronization at baseline and final assessment. Shown is circadian malsynchronization, defined as the absolute phase angle (mean ± SE hours) between aMT6 acrophase and mid sleep, determined at baseline and following the light treatments. A significant increase in malsynchronization was found.
Figure 6
Phase dispersion at baseline and final assessment. Shown is phase dispersion, defined as the absolute number of hours (mean ± SE) between aMT6s acrophase and the median aMT6s acrophase, determined at baseline and following the treatments.